Compass

[AC30301998]

Dear Navigational & Nautical Friends

Mounting a Compass


A few years ago I was given a Richie Voyager S-87 Surface Mount Compass as a gift. I currently own a 21? cuddy cabin. The bows top deck is a common walkway; where the middle section of the windshield flips open and allows walking access into the cockpit. This common walkway is the only section of the dashboard over the keel of the boat. For sure the compass would be in the way of walking traffic. I really would like to mount the compass right in front of the helm on the starboard side of the boat. The only electronic components that are place on the driver?s dash are my instrument gages and the rack and pinion steering.

But if my compass is not in line with the keel of the boat, it won?t track the same heading as the compass. Right?

Is there a way I can off-set the compass enough to have it in the center of the side helm seat and still have it track the same course as the boat? We?re talking maybe 2 feet off center with the keel.


If not. Can I build a box that would hold the compass and sit center (keel) of the dash? Something like a jig on the dash that centered the box every time you set it down. How accurate would the compass be, if I kept moving it around every time when needed?

I don?t go out on deep sea, of course it?s only a 21? cuddy cabin, but I do go out a lot at night and in fog conditions. To me installing a compass that doesn?t give you the true heading is pointless and can be dangerous.

Any Answers, comments, and concerns would be greatly appreciated!!!

Thanks for reading my long post
AC30301998

 

[Boatist]

Re: Compass

Unless your going to mount a Flux gate compass then the compass must be mounted ahead of the Helm Station. If you mount it over the keel of the boat and the helm is on the Starboard side like most boats then there will be no way to read it correctly.

The compass need to be mounted directly ahead of the helm. It must be positioned or rotated so that the reading the same as if it was in the center of the boat over the keel.

What I mean is if your boat is pointed North and your stand in your boat with the compass held in front of you over the keel and rotate the compass to read north. Then takes two steps to your right still holding the compass in front of you then it will still read North.

So hold your compass in front of the helm station and make sure as you hold it there your do not see any large changes in heading like you would see from and Motor or Speaker. Then set it down and make sure your can see it from your helm station. Then cut or drill any required mounting holes. Hold it down with stainless steel screws as they are non magnetic and will not affect the reading.

The last steep is to swing the compass. Point the boat North and make sure it read North. Swing the boat to head South and make sure it reads South. If not then it needs to be adjusted. Read the adjustment instruction carefully. Once you get North and South reading right then do the same with East and West. There will be a seperate adjustment for East and West.
Since the adjust also can affect North and South some then you need to recheck them..

You can make these adjustments at a dock that is lined up North and South then West and East. Some charts will have either a dock identified or a set of buoys that can be used to make sure of the alignment.

It can be on the trailer in a parking lot but remember the trailer can cause some compass defelections. In my case My trailer had no effect at all.

It is important you get the compass as close as possible in case some day your have total electronics failure and have to use charts and compass to get home.

Still electronics is a good way to verify your compass setting when your done.

One last point when setting up your compass make sure you adjusting to magnetic North not true North.

 

[BWR1953]

Re: Compass

Just make sure the lubber line on your compass is parallel with the keel and you should be good to go.

 

[Ned L]

Re: Compass

The simple answer is: The Best place to place the compass IS directly in from of the helmsman. (This way you avoid any parallax (what Boatist was referring to)). As BRW1953 said, make sure the lubber's line is set correctly (look it up, this is simple). A correct installation will include 'boxing the compass' and creating a deviation table (what Boatist is talking about), this is a bit involved & takes some time & patience (look it up & read about it). This is probably not necessary for the great majority of small pleasure boats today unless you've got something near your compass that is really screwing it up. When installing your compass and other accessories near by keep in mind that the biggest problem will be caused by magnets from audio speakers (watch out for speakers mounted near by & below it in any cabin area). Rare earth magnets (may be in some speakers or microphones can cause problems from greater distances). -- Generally, the things that will affect a compass are ferrous metals (iron, steel) and magnets. Aluminum, brass, and most stainless steels have no effect.

 

[special_kaye]

Re: Compass

Generally, the things that will affect a compass are ferrous metals (iron, steel) and magnets. Aluminum, brass, and most stainless steels have no effect.

And refrigerators. Bought a new compass yesterday and had it in hand when I walked by the refrigerator. Swung 90 deg off line up, then swung back as I moved away. So, if you want to find your way out of the kitchen, don't mount the compass near the refrigerator.